1. Field of the Invention
The present invention relates to a region extraction apparatus, a region extraction method, and a computer program product.
2. Description of the Related Art
Conventionally, in production printing, a technology (printing with high-speed copiers for the commercial printing market and the office printing market) has been known in which printing data is created to apply a special effect to a printed image by changing its glossiness with clear toner (transparent toner) or by using a spot color such as a metal or fluorescent color.
Furthermore, a method in which a user specifies a few regions to which the user desires to apply a special effect, and a system automatically extracts a region similar to the specified regions by a similar region search using a local feature value, and automatically extracts the contours of the region by a contour extraction process (graph cuts or the like) is already known as a method for identifying a region to which a special effect is to be applied.
Furthermore, Japanese Patent Application Laid-open No. 2011-002965 discloses, for the purpose of realizing a highly accurate image search without depending on a change in the background of an object, a method for specifying a contour line that separates an object of a query image from a background, extracting a plurality of local feature values of the query image, searching a database with a local feature value of an object region only, acquiring a plurality of candidate images, subsequently calculating an element feature value of each sub-region of the query image, recalculating an element feature value of each sub-region including its contour line using an element feature value of a neighboring sub-region of the sub-region for the query image, comparing, only for the object region, the recalculated element feature values of the sub-regions of the query image with element features values registered in the database of the candidate images, further calculating the similarity of the candidate images to the query image, and selecting and outputting the image with high similarity as a search result.
However, the technology in which a few regions to which a special effect is applied are specified and a similar region search or the like is performed as described above, and the technology of Japanese Patent Application Laid-open No. 2011-002965 detect only a few feature points in, for example, an image such as an image of a water droplet on a leaf where automatic extraction is hard, and therefore cannot obtain a sufficient number of similar regions. Moreover, there is a problem that if a threshold value is lowered to increase the number of detections, the number of noise detections increases, and a problem that not the contour of the droplet but a highlight portion is falsely detected, or the like occurs.
In view of the above, there is a need to provide a region extraction apparatus, a region extraction method, and a computer program product that can accurately extract a predetermined region in an image.